In the production of folding banquet tables, it is well known to affix a frame or apron, of generally rectangular shape, to the underside of a tabletop to lend rigidity and reinforcement to the table. One machine commonly used to form aprons is known as a fixed single-headed bender, in which a continuous length of metallic stock material is first delivered along a guide path on a platform. The stock material is bent, usually at the discretion of an operator, at certain intervals into a rectangular configuration and cut to form the last side of the apron. The bent material is then transferred, sometimes manually, to another station where the cut ends of the apron are suitably formed together by a key, splice or welding to complete the rectangular frame assembly. In some instances, the stock material is supplied in discrete lengths so that the cutting step may be eliminated.
Other apron forming machines, known as two-headed benders, utilize a pair of spaced bending units which are movable along a single axis of an elongated frame component and cooperable with a clamping structure to form a first pair of right angle bends near the outer ends thereof. Once the initial pair of bends is formed, each of the bender heads is moved inwardly, the frame component is clamped and another pair of right angle bends is formed. As in the single headed bender, the bent framework is then transferred to a different location where the ends are joined together.
While each of these prior art frame bending machines can be utilized to effect bending of various frame components, they each have limitations which make them less than ideal for certain situations. For example, in using both of the machine types described above in the high volume production of table aprons, it is generally necessary to employ 1-3 workers who are responsible for the bending and cutting operations, the material handling of the bent frame and the final end forming function. Even with multiple workers, it has been found extremely time consuming to turn out sizable quantities of completed aprons. Regardless of the prior art bending designs, no provision has been made to efficiently bend a pair of apron sections in a manner such that the bent ends can be juxtaposed and fastened together on a support surface common to the bending operation. In addition, there is no known apron forming apparatus which provides a minimal mechanical set up for size changes in the frame or apron.
There are other drawbacks which arise in the use of these prior art frame bending machines. In the case of the single-headed bender, far too much emphasis is placed on the operator's judgment to make strategically positioned bends. With respect to the two-headed bender, long lengths of minimally supported stock material tend to bow in the middle between the bending units due to gravity, creating an irregularly shaped apron.
Although various bending systems have been devised for forming rectangular frames, there remains a need for a more efficiently designed apron forming apparatus which will satisfactorily combine bending and end forming functions in a common plane. Accordingly, it is desirable to provide an apron forming apparatus having a four headed bender design, each of the benders being adjustable along two separate axes in the common plane so as to readily accommodate different apron sizes. Likewise, it is desirable to provide an apron forming apparatus which will operate to accurately bend and position the ends of a pair of apron segments in an overlapping relationship which will facilitate an efficient joining of the segment ends to complete an apron. It is also desirable to provide an apron forming apparatus which will significantly reduce the cycle time to produce any desired apron size.